I happen to have this similar issue but it was the first +200% vets from this event. Too much failure.

dang stop vetting to 200 then

ACtually it was with 100 vets and burning gives no result

i had similar experience as you. my heart almost stopped for the huge amount of experts loss with unsuccessful conversion.

Welcome to navyfield, you never know what you are going to get, yet even what the +200%means........ The only way to really get good rolls is to have a +200% event and use premium, but if you are like me and dont bother paying for prem just enjoy watching vets get burnt through. My only reccomendation would be to vet like crazy early on say lvl 55-65 and then aa using PCA's or another CA until lvl 70-75ish to get back your vets. That worked well when i was making my cv crew.